Chapter 11, Problem 67PQ

Assume the pucks in Figure P11.66 stick together after their collision at the origin. Puck 2 has four times the mass of puck 1 (m₂ = 4m₁). Initially, puck 1’s speed is three times puck 2’s speed (v_1i = 3v_2i), puck 1’s position is ${\stackrel{\to }{r}}_{\text{1}i}=-x_{1i}\hat{i}$, and puck 2’s position is ${\stackrel{\to }{r}}_{\text{2}i}=-y_{2i}\hat{j}$. a. Find an expression for their velocity after the collision in terms of puck 1’s initial velocity. b. What is the fraction K_f/K_i that remains in the system?